Fluid flow controllers of the type described above are known in the art and are used, for example in air technical structural components in climate control systems including air conditioning systems, for example in air flow ducts, air outlets and similar components, open loop or closed loop type for controlling flow volume and/or flow direction. These air technical components are simply referred to herein as components. Technical equipment in buildings comprises such components which must be controllable in response to the temperature of the air passing through the components on the one hand and in response to the temperature in a room or space into which the air passes through the components such as an air outlet. A suitable control value for the adjustment of the component or structural units comprising such components is frequently a temperature difference between the temperatures of the two fluids involved, e.g. hot air and cold air. Compared to the absolute temperature values, the temperature difference between these values is a substantially more important value for the climate control of a room because the temperature difference gives information whether the room is being heated or cooled. In case the temperature difference is positive, heating is involved. If the temperature difference is negative, cooling is involved.
In connection with air outlets such as air flow twister outlets installed in a ceiling and air source outlets or vortex outlets installed near the floor, it is necessary to vary the flow direction of the air discharge from the outlet depending whether the air has a temperature higher or lower than the temperature of the air in the room. The changing of the flow direction is necessary in order to meet modern comfort requirements, for example in order to divert a cold air flow away from customers or personnel. Such air flow control is also important for achieving an energy efficient climate control of an enclosed space. In connection with ceiling outlets, drafts must be avoided by diverting the cooled air horizontally along the ceiling so that the cold air may sink uniformly down to the floor. On the other hand, warm air must be blown downwardly for a rapid heat-up of the room. In connection with so-called air source outlets installed close to the floor, it is necessary to direct cooled air at an angle upwardly so that the cooled air can then at some distance from the outlet sink down to the floor again. In this manner it is possible for the added air to achieve a large reach without the need for large air exit velocities. Low air exit velocities are desirable for the replenishing of the air in a room with fresh air. However, if heated fresh air is to be introduced through an air source outlet, it is necessary to direct the heated air at an angle downwardly in order to heat the large heat storage mass of the floor on the one hand and to prevent an instantaneous rise of the warm air to the ceiling because such a rise substantially reduces the heating efficiency of the warm air.
Conventional heating control devices are generally equipped with two electric or electronic temperature sensors, one of which measures the room air temperature and the other measures the temperature of the fresh air. Depending on the temperature difference value, the control is effected generally with an electric motor or occasionally with a hydraulic or pneumatic drive functioning either as a volume flow closed loop controller or as an adjustment member for changing the flow direction of the air exiting from an outlet. Conventional adjustment mechanisms and their drive are relatively complicated and hence expensive because, on the one hand such closed loop control devices include a substantial number of structural components and require an expensive set of electrical conductors, including conductors for supplying energy to the controllers such as an electric motor for performing the adjustment.
Adjustment devices not requiring any additional energy for the control operation are also known. Such devices perform the adjustment of an adjustable component solely in response to the measured temperature of the fresh air. The adjustable component is operated by means of a single expansion drive arranged in the fresh air volume flow. Such an expansion drive position limits the response of the expansion drive to the temperature of the fresh air and the difference between the fresh air and the room temperature cannot be used for the purpose of flow control. The disadvantage of a single expansion drive is the fact that the same fresh air can have the same temperature for heating purposes and for cooling purposes. Thus, if in the example the fresh air temperature is 22.degree. C. and it is assumed that a heating is required, it will be necessary to adjust the component of a ceiling twister or vortex outlet so that the fresh air is directed perpendicularly downwardly into the room having, for example a temperature of 18.degree. C.
However, if the room temperature happens to be already 25.degree. C., for example in the summer, the fresh air temperature will have the same temperature of 22.degree. C., but a heating is not involved. Rather, a cooling is needed. Thus, if the adjustment of the exit flow direction depends solely on the temperature of the fresh air, the cooling air of 22.degree. C. will again be directed perpendicularly downwardly, whereby drafts are generated in areas below the ceiling twister or vortex air outlets. Further, the temperature distribution throughout the room will vary widely with localized warm high temperature peaks near the ceiling. Actually required in such a case is a substantially horizontal flow direction of the cooled air along the ceiling to distribute the cooled air uniformly over the ceiling and thus over the room cross-sectional area to permit the cool fresh air to sink down uniformly throughout the room. Such an air distribution cannot be achieved with an adjustment by an expansion drive that is solely dependent on the fresh air temperature.